The great Mesabi Range began in this sea, which contained concentrations of iron and silica. The iron and silica settled to the bottom of the sea and formed thick layers of iron-bearing sediments. As time went on, the sea disappeared, leaving these sediments buried under thousands of feet of sand, clay and mud. As a result of this deep burial, the iron-bearing sediments were subjected to heat and pressure which transformed them into a hard, flinty rock we call taconite. Taconite consists primarily of chert, a form of silica, and of magnetite, a black, magnetic iron mineral.
During the long period since its formation, Mesabi taconite has been subjected to a variety of geologic processes that have altered its character. Today, however, the great bulk of the Mesabi Range iron formation remains as hard, magnetic taconite – enough to last hundreds of years using conventional mining methods. With new mining methods being developed and in progress, the future of iron mining in northeastern Minnesota is bright.
Iron is one of the most abundant metals found on earth. Close to five percent of the earth’s crust is iron. These iron minerals are typically mixed with clay, sand, rock or gravel, making iron a very common mineral – common enough to be found in your backyard. But, only when the iron is concentrated in large enough quantities and sufficient quality can it be mined for commercial use.
Use of iron ore dates back more than 5,000 years, and as needs for iron have grown, iron ore deposits have been found all over the world. Minnesota has the largest deposits of iron ore in the United States and northern Minnesota has been mining iron ore for 130 years (26 years after Minnesota became a state in 1858).
Perhaps the first use of iron ore was for the bright red and yellow colors that characterize many iron ores. Even today, iron ores are used in a minor way for paints and dyes. But the major use of iron has been as a metal – for tools and implements, for structures, and in modern times, for all the steel goods made from iron.